Periprosthetic Fractures of the Hip

Acetabular Fractures

  • Occurs during cup impaction or cup removal in revision surgery
  • Often identified post-operatively
  • Must have a high index of suspicion for at-risk cases

Intra-operative Risk factors:

  1. Uncemented cup
  2. Press fit cup
  3. Under-reaming by >2mm
  4. Impaction of the cup in a position different to that reamed
  5. Poor bone quality – osteoporosis/Paget’s disease
  6. Revision surgery during component extraction and impaction

Post-operative Risk factors:

  1. Trauma
  2. Poor quality bone
  3. Infection, osteolysis, loose implants

Classification:

There are classification systems (Paprosky etc.) but the key questions are:

  1. Is the fracture displaced?
  2. Is the cup stable?
  3. What is extent of fracture? (Wall fracture; column fracture, discontinuity)
  4. Is there adequate bone stock? (>50%)

Management:

Principles are essentially the same for intra and postoperative fractures

  • Undisplaced with stable cup:
    • Supplementary cup screws, restricted weight bearing and vigilance
  • More extensive fracture with stable cup:
    • Prophylactic fixation if intra-operative then standard cup with screws
    • If postoperative: vigilance for migration and low threshold for revision
  • Displaced with unstable cup:
    • Fix fracture with screws or recon plate if necessary
    • Ream line to line; supplement with cup screws
    • Consider jumbo, trabecular metal cup if some bone loss
  • Posterior column fracture with unstable cup:
    • Fix fracture with plate then use large trabecular metal cup with screws
  • Pelvic discontinuity:
    • May not be stabilisable with plating alone
    • Be prepared to supplement with cup cage construct or allograft
  • Bone loss associated with any situation:

    • < 50% bone loss

      • Large trabecullar metal cup with screws, augments, impaction grafting options

    • 50% bone loss

      • Consider cup cage constructs with impaction grafting, cement, trabecullar metal or supplementary allograft options

Femoral Fractures

Intra-operative Risk Factors:

  • Anatomic variants to proximal femur
  • Excessive femoral bow (e.g. Paget’s)
  • Poor bone quality (e.g. osteoporosis, rheumatoid)
  • Uncemented stems esp. fully porous coated
  • Cylindrical non-anatomic stems
  • Revision surgery during cement removal and large stem insertion

Postoperative Risk Factors:

  • Trauma
  • Infection, osteolysis and loosening
  • Stress risers from stem design
  • Osteoporosis

Typical fractures around different stems post operatively are:

  • Extensive coated – at tip or distal
  • Proximal coated – where porous coating is jammed into femur (B type)
  • Cemented – same mode as extensive coated due to load distribution
  • Cemented tend to fracture later than uncemented
  • Cemented B type due to resorption of cement bone interface with time

Classification – Vancouver Post-operative and Intra-operative:

Postoperative:

  • AG or AL Treat depending on degree of displacement and dysfunction
  • Options include TBW; Claw plate; cabling etc.
  • B1: At level of stem or just distal with well fixed stem and good bone
  • B2: Loose stem; good bone stock
  • B3: Loose stem with poor bone stock
  • C: Distal to stem – does not affect stem stability

Intra-operative:

  • Type A, B and C by location and divided into subtypes
  • Type A:
    • A1 Leave alone or bone graft
    • A2 Cerclage wiring or claw plate
    • A3 As above or use long stem plus ORIF if stem destabilised
  • Type B:
    • B1 Make sure stem bypasses perforation by 2 cortical diameters
    • B2 Cerclage wiring or plating and bypass by 2 cortical diameters
    • B3 Lean towards plating =/- strut grafts and bypass by 2 diameters
  • Type C:
    • C1 Non-operative or strut grafts and cables to prevent propagation
    • C2 ORIF with plate overlapping stem
    • C3 As for C2 but may also use strut grafts
  • Revision stems:
    • Need 4cm of isthmus to gain reliable hold and should pass the most distal defect by at least 2 cortical diameters
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